Activities of interstitial elements inside heat-resistant steels, filler alloys, and weld electrode materials
|Jiri Sopousek 1, Zdenek Hodis 2|
1. Masaryk University, Faculty of Sciences, Kotlarska 2, Brno 61137, Czech Republic
Steels are popular engineering materials for industrial use. They are usually alloyed with the other elements (Me: Cr, Mo, V, W, Nb, ... and N) in order to improve the mechanical and corrosion resistance properties.
The modern high-resistant steels (P91, P92, E911, VM12)  reached the high strength up to 100MPa at 575-650°C. It is no rare case that these steels have to be weld joined with the other steels, which have different compositions (T/P22, T/P23, T/P24, …). In the case of dissimilar weld joints , the mechanical properties usually take a turn for the worse because the phase microstructure changes caused by long-time diffusion during exploitation at high temperature . The most important diffusing elements are the carbon and the nitrogen for the steels. The diffusion flux of these light elements is in close relation to their thermodynamic activities.
The heat-resistant steels, filler alloys, and welding electrodes can be thermodynamically treated as Fe-Me-N-C based closed systems. Phase diagrams and temperature dependent carbon and nitrogen activities of the steels can be calculated using CALPHAD approach .
In this contribution, the CALPHAD method is applied. Examples of phase diagrams, temperature dependences of the carbon and nitrogen activities are calculated, plotted, and discussed.
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Presentation: Poster at E-MRS Fall Meeting 2006, Symposium I, by Jiri Sopousek
See On-line Journal of E-MRS Fall Meeting 2006
Submitted: 2006-05-10 08:39 Revised: 2009-06-07 00:44
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